In Elizabethean England, actors formed companies. For example, Shakespeare was a member of The Lord Chamberlain's Men which was later renamed The King's Men when they got royal patronage from James I.

Shakespeare was a shareholder which meant that he owned a share of the company. These share holding actors were like mastercraftmen. When a shareholding actor left, he would sell his share to another master actor. For example when Will Kemp left, he sold his share to Robert Armin. Since each of these comic actors were different, the role of the fool changed in Shakespeare from the buffoon to the thoughtful fool. When Shakespeare retired, he sold his share to John Fletcher, a playwright.

Other parts were taken by journeymen actors. It could be argued that the apprentices were the young boys who played the young female roles since it was not thought to be fitting for females to be on stage. The theatres were located across the Thames in an area of drinking, gambling, bear & bull baiting, houses of ill repute, etc. Not a fit place for a lady.

Like actors today, these actors would be trained to use their voices. Physically they would need to learn to move effectively. They would learn how to dance and use various weapons. An actor whether then or now must be phyically fit.

Since the plays were written in blank verse, it was easy for them to memorize. They would need to keep somewhere between 30-40 plays in their head since a play could be revived upon request and there were no brush-up rehearsals.

There was no director as we have today. Stage directions in Shakespeare are contained in the language itself. Since these actors were master craftsmen, they understood how this worked. If they had a question, Will was right there to ask. The stage directions we find in todays Shakespeare were added by editors. Shakespeare wrote only a few. The most famous is "Exit Antigonus followed by a bear" in The Winter's Tale.

Compared to today, there are companies like the Royal Shakespeare Company in Stratford-upon-Avon where a company of actors work with a director to explore how to perform Shakespeare's plays. However they do not own shares in the company but are contracted for a season. This is also true of the current company of actors at Shakespeare's Globe in London.

Actors then and now basicaslly do the same things. They train and take classes. They rehearse and go home and learn their lines. They study.